circleci: Attempt to fix "Cannot allocate memory" when building CMake

This commit attempts to fix the following error by limiting the number
of parallel build and link jobs.

  [...]
  cmcompress -I/work/src/Source/CTest -I/work/src/Source/CPack -O3 -DNDEBUG   -std=gnu++17 -MD -MT Source/CMakeFiles/CMakeLib.dir/cmLocalGenerator.cxx.o -MF Source/CMakeFiles/CMakeLib.dir/cmLocalGenerator.cxx.o.d -o Source/CMakeFiles/CMakeLib.dir/cmLocalGenerator.cxx.o -c /work/src/Source/cmLocalGenerator.cxx
  /work/src/Source/cmLocalGenerator.cxx:2901:1: fatal error: error writing to /tmp/ccLGyPoR.s: Cannot allocate memory
   }
   ^
  compilation terminated.

Author: jcfr

CMakeLists.txt

@@ -169,6 +169,19 @@ if(CMakePythonDistributions_SUPERBUILD)
           )
         message(STATUS "SuperBuild -   CMakeProject-build - OPENSSL_ROOT_DIR: ${OPENSSL_ROOT_DIR}")
       endif()
+      foreach(var_name IN ITEMS
+        CMAKE_BUILD_PARALLEL_LEVEL
+        CMAKE_JOB_POOLS
+        CMAKE_JOB_POOL_COMPILE
+        CMAKE_JOB_POOL_LINK
+        )
+        if(DEFINED ${var_name})
+          list(APPEND _cmake_cache_args
+            -D${var_name}:STRING=${${var_name}}
+            )
+          message(STATUS "SuperBuild -   CMakeProject-build - ${var_name}: ${${var_name}}")
+        endif()
+      endforeach()
 
       ExternalProject_add(CMakeProject-build
         SOURCE_DIR ${CMakeProject_SOURCE_DIR}

scikit-ci.yml

@@ -11,7 +11,7 @@ before_install:
   circle:
     environment:
       PATH: /opt/python/$<MANYLINUX_PYTHON>/bin:$<PATH>
-      SETUP_CMAKE_ARGS: -DOPENSSL_ROOT_DIR:PATH=/usr/local/ssl
+      SETUP_CMAKE_ARGS: -DOPENSSL_ROOT_DIR:PATH=/usr/local/ssl '-DCMAKE_JOB_POOLS:STRING=compile=4;link=3' -DCMAKE_JOB_POOL_COMPILE:STRING=compile -DCMAKE_JOB_POOL_LINK:STRING=link
 
   travis:
     osx: